This program project has two interrelated long term goals to understand: (1) how trisomy 21 leads to Down Syndrome; and (2) in as much detail as possible the organization and evolution of the DNA of chromosome 21. Progress will be highly synergistic and best optimized by the united multifaceted approach. This endeavor should have great significance for understanding how the human genome is organized and functions during human development and for delineating approaches to gene mapping which could be applied to the entire human genome. Two projects (Patterson, Kao) focus mainly on somatic cell genetics and molecular biology to create a detailed physical map of chromosome 21. Techniques include preparation of somatic cells hybrids containing only portions of chromosome 21, microdissection and microcloning of regions of chromosome 21, and regional mapping of DNA sequences using standard pulsed-field gel electrophoreses. The chromosome 21 translocation breakpoints in these hybrids will serve as molecular landmarks for a physical map of chromosome 21. Dr. Gardiner will create a library of large (>IOOkb) DNA fragments of chromosome 21 in an early manipulatable form in a yeast host and use this library to isolate and analyze specific regions of chromosome 21, allowing direct study of any area of chromosome 21. Drs. Jones and Drabkin will study gene regulation on chromosome 21 which has to do with immune response and leukemia using somatic cell genetic and molecular approaches. They will take interspecific human/Chinese hamster cell hybrids containing chromosome 21 translocation chromosomes as a part of their work, which will be used for mapping. Dr. Drabkin's work will focus on translocations associated with leukemia and mechanisms by which extra copies of genes on chromosome 21 may lead to leukemia. Dr. Jones project will focus on induction of the interferon response and similar immunogenetic studies of other cell surface molecules, i.e. beta amyloid. Dr Law will isolate gene sequences on chromosome 21 and study the possible role of repeated sequences in gene regulation. She will use molecular cloning, DNA sequencing and in situ hybridization. Genes of interest and blocks of genes on chromosome 21 regions will be introduced into cells in culture and ultimately into experimental animals to understand how these genes might, when present in 3 copies instead of the normal two, lead to certain aspects of Down Syndrome.